Wing tip design?

Wing tip design?
View related threads: (in this forum | in all forums)

Logged in as Guest

Users viewing this topic: none

Printable Version

Fei Bao Velox - Pro Built - ARF
Seller: SinCityJets
Details: $2,200.00 | 1/4/2009 | Classified Ad
We will rotate YOUR AD in this spot if you select "Forum Featured" when placing or editing your ad!

All Forums >> RC Airplanes >> Aerodynamics >> Wing tip design?

Page: [1] 2 next > >>

Login

Message

<< Older Topic Newer Topic >>

Wing tip design? - 1/31/2002 8:49:06 PM

Volfy

Posts: 3227
Joined: 1/4/2002
From: Houston, TX, USA
Status: offline

I read in Ed Moorman's RC University http://members.home.net/rcuniversity/WingTips.htm about his experiments with wing tip plates and am very impressed. However, even though it makes very good sense, it conflicts somewhat with some of the older NACA studies I've read, which indicated that a rounded thin wing tip has less induced drag than a thicker or blunt wing tip. Or does it? Perhaps a blunt wing tip generates more wake vortices, and thus induced drag, than a "squared off" wing tip with a thin tip plate attached. Then again, perhaps the scale factor is at play here, since the NACA studies are on full scale aircrafts.

I'm trying to decide what to do for the wingtips of a couple of ARF wings after I ditch those cheapo plastic shells. Any suggestions? References or articles I can go read?

Wing tip design? - 1/31/2002 10:19:56 PM

Posts: 7
Joined: 1/31/2002
From: , ,
Status: offline

The basic answer is to do whatever you feel like.

I have been an aeronautical engineer for 20+ years, and have finally come to the conclusion that if some wing tip design really was better, it would be obvious and people would not still be arguing about it all the time.

Besides on an ARF, you are not talking about having outstanding aerodynamics to start with, and even the best of tips wont make a noticeable difference.

bob

(in reply to Volfy)

Model Aerodynamics - 1/31/2002 11:06:01 PM

Posts: 2485
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline

I have to agree with Bob. There may be differences that could be measured with some scientific instrument, or shown in a wind tunnel, but what can you SEE or "feel" when flying the model?

I've done a kabillion experiments over the years with models, and I think that at the Reynolds numbers we usually fly at, these details are negligible. However, you could make a plywood plate on the wingtip, and try attaching different configurations yourself, and see if you agree. (Wingtips aren't too time consuming to make.)

_____________________________

Mike James
RC Design and Building - www.nextcraft.com

(in reply to Volfy)

Wing Tips - 2/1/2002 6:10:30 AM

Posts: 3725
Joined: 1/5/2002
From: Shalimar, FL, USA
Status: offline

All of my conclusions were based on actual model tests.

In some cases it is difficult to apply full scale aerodynamics. As one reply already stated, we are operating in such a low Reynolds number area we are essentially off the chart. This is the reason the large models fly better, and also the reason the TOC type competitors fly as large a model as allowed. They just fly better.

As for the wing tips, try several of the different types and note the results for landing speed, stalls, spins, roll rate and others you can think of. I think you'll find the end plates give a higher roll rate and a lower landing speed.

I published this same data in my R/C Report magazine column, "Fun Aerobatics," and two modelers tried experiments with plates and sent me the results. Both agreed on a higher roll rate and a slower landing speed.

_____________________________

Ed Moorman, AMA 553, KD4QBM, Revver Bro #156
R/C Report Magazine, Fun Aerobatics Column

(in reply to Volfy)

Wing tip design? - 2/1/2002 10:24:23 AM

Volfy

Posts: 3227
Joined: 1/4/2002
From: Houston, TX, USA
Status: offline

Ed, I didn't know you frequent this joint. Then again, I haven't been here long enough to know much.

I'd agree that for the 1.20 size and under, just about any wing tip design will work fine. Heck, I remember reading in an article that some guy built a fun-fly with an airfoil shaped from his wife's stiletto. So many of the smaller models are overpowered and flying on the motor more than on the wing anyway.

I'm a little rusty since my undergrad Fluid Dynamics classes 15yrs ago, but for the bigger models (1/4 scale and up), the Reynolds number do begin to approach those of full scale aircrafts. Of course I don't mean 747s, but the RVs and Cessnas aren't all that much bigger than some of these newer 1/3 and 40% ARFs.

As I have not progressed too far beyond the basic RC flying skills stage, my main interest is to improve low speed and stall characteristics. In another words, keep the plane flying good and me out of trouble. That is why Ed's article grabbed my attention. I guess I'll just have to keep the wingtips squared off and try a few simple bolt-on tip designs to see what happens. Thanks all for the comments.

(in reply to Volfy)

wing tips - 2/1/2002 11:21:51 AM

Posts: 1591
Joined: 12/11/2001
From: Merrimack, NH, USA
Status: offline

If it's worth your while to search on that other forum (the slow one) you can probably find the post within the last year or so concerning an end-plate experiment in which a modeler fitted removable end-plates, trimmed the plane with both end-plates on, then removed one and flew again. To get the model re-trimmed in the roll axis he reported two clicks of aileron correction were necessary. Two clicks is not a whole lot, but it is a more tangible result than many other popularly debated design mods.

(in reply to Volfy)

Wing tip design? - 2/1/2002 12:07:07 PM

Posts: 7
Joined: 1/31/2002
From: , ,
Status: offline

Ed wrote

>All of my conclusions were based on actual model tests.

Sure, but you didnt actually measure the drag on any of them. On virtually any full scale airplane (i.e. where performance is worth money) drag is important, and tip plates are actually very draggy. Yes, you will get some aileron effectiveness, and you can cut the stall speed, but you can get the same results with less drag by other methods.

Winglets can be thought of as tip plates "done right", but even then, its usually better to just increase the wing span a bit. The problem with winglets is that they work well at only one flight condition. Fine for retrofitting airliners, but marginal on sailplanes.

As for the Reynolds Number comments, yes we have sort of low RN, but for most RC power planes, its not THAT low and the basic principles still apply. (FWIW, I do a lot of engineering work on Mars airplanes, and there the RN is pretty low.. 1/5 to 1/10 of your typical RC .40 sport plane, but transonic Mach and things are pretty different there).

bob

(in reply to Volfy)

Wing Tips - 2/1/2002 9:25:08 PM

Posts: 3725
Joined: 1/5/2002
From: Shalimar, FL, USA
Status: offline

You are still thinking like a full scale flier. Except for racers, sailplane fliers and maybe a few experimenters, nobody gives drag a second's thought. Certainly not the vast majority of RC fliers who fly sport and fun fly planes. Drag! We hover planes. that's power. Drag-bigger engine. Besides, if we were really concerned about drag, we wouldn't ever fly a biplane!

As for winglets, I have seen them on sailplanes, a couple. But other than that, let's get serious here. We fly upside down. You need, at least, I need something that works both ways, upright and inverted. In addition, I would kill winglets on my planes with hangar rash. They just aren't practical on sport RC planes.

End plates, on the other hand, work on RC models. I'm an engineer so I know what's in books, but I am also a long time modeler (I flew my first powered plane in 1950), so I also know what works. You need to slap on some big plates and see what happens. Do the experiment.

I published information on end plates in my R/C Report column several onths ago. Recently I had 2 fliers send me data and photos on their experiments. These will be published in the April issue. One plane was a mini-Wonder, a scaled down version of a Sig Wonder for a 400 electric. It was a tip stalling fiend. The plates stopped the tip stall and increased the roll rate. The second plane was an RCS 1.4 powered, Goldberg Ultimate. The owner reported a much slower and nicer landing.

Try end plates. Naturally, they don't solve everything, but they do help in certain areas. Send me the results of your tests and photos and I'll publish them.

_____________________________

Ed Moorman, AMA 553, KD4QBM, Revver Bro #156
R/C Report Magazine, Fun Aerobatics Column

(in reply to Volfy)

End Plates - 2/2/2002 1:00:33 AM

Posts: 2485
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline

Right, Ed!

A rather well-known example of the effectiveness of end plates is on the original (.40 size) "Hots". That model had unexpectedly good slow speed characteristics, and VERY fast roll rates. Mine looked like a cartoon when you rolled or snapped it at high speed.

Ed,

Can you be of assisstance with my "wing and stabilizer arrangement for aerobatics" post, also in this "Aerodynamics" list?

_____________________________

Mike James
RC Design and Building - www.nextcraft.com

(in reply to Volfy)

Wing tip design? - 2/2/2002 1:37:15 AM

Posts: 7
Joined: 1/31/2002
From: , ,
Status: offline

Ed wrote:
You are still thinking like a full scale flier. Except for racers, sailplane fliers and maybe a few experimenters, nobody gives drag a second's thought.

If you go back to the first post in this thread, the topic of induced drag came up.. I was responding to that. Also, your web page makes a lot of claims about low drag. My point is that all the real measurements don't back up your claims. I agree, if you don't care about the drag, tip plates can have some advantages.

Ed said:
Besides, if we were really concerned about drag, we wouldn't ever fly a biplane!

You can do efficient biplanes. For some cases they can have performance advantages over monoplanes.

Ed said:
I'm an engineer so I know what's in books, but I am also a long time modeler (I flew my first powered plane in 1950), so I also know what works.

Ok you have be a few years on me. (I was born in 51 and didnt get around to power free flight until 1959). But I also have designed planes that got a few world records and a Harmon trophy, so yes, I have some clue about what works too.

bob

< Message edited by bobparks -- Feb 4 2002 6:01PM >

(in reply to Volfy)

Wing tip design? - 2/15/2002 8:05:36 AM

LDaba

Posts: 179
Joined: 2/8/2002
From: Queens, NY, USA
Status: offline

I have read Ed Moorman's article on end plates. Does anyone else have firsthand experience with these? I am planning to use them on a sport plane. They will attach with 4 screws,so I can add or delete them at the field. I am new to these, and I am looking for input.
I have average flying skills and would not want to get in over my head.

By average skills, I mean I can do the basic school maneuvers in a left or right hand pattern and can do a reasonable performance of advanced maneuvers.
Thanks in advance. Happy landings Tony

_____________________________

Keep 'em Flying
Anthony Puleo, AMA11973

(in reply to Volfy)

Wing tip design? - 2/15/2002 10:48:18 AM

Posts: 7
Joined: 1/31/2002
From: , ,
Status: offline

Tony,

The tip plates can increase aileron effectiveness, but as long as you are comfortable flying normal maneuvers reasonable size tip plates wont do anything to make the plane hard to fly. (If you put on tip plates that are a couple feet high on a .40 size trainer, it may get a bit wierd ;-) )

So, go try it, have fun, and post the results here.

Bob

(in reply to Volfy)

Wing tip design? - 2/15/2002 11:14:44 AM

Posts: 656
Joined: 12/3/2001
From: Minot, ND, USA
Status: offline

The most effective aileron's are sealed Aileron's! Tip plates can control lateral movement of the wing as does a rudder. Tip plates are not creating dirty air across a control surface so they have no viable use other than a stabilizer ie. Rudder.

A 100% totally clean wing will have lousy control capabilities at various speeds. Thats why Aircraft have what is called a Vortex Generator. What this?(It's a bunch of little piece's of metal sticking up in different directions to dirty the air prior to it getting to the control surface.) Dirty Air.

Say you purchase an ARF or build any of the funfly style aircraft, of any performance nature with Flat wing tips. You take it to the field and it just won't stay put on knife edge. Always wants to fall out, your always fiddling with the ailerons trying to maintain a crisp knife edge. You now put some winglets on it and it holds steady. Why? Because you've created two more rudder surfaces.
Now you take that same aircraft and buy some clear Ultra-coat if you have an Arf. And you seal the Whole length of the Aileron's and the Elevator. Your Airflow across these surfaces no longer have the gapppppppping Hole/slots and I'll gaurntee(Texas Draw LOL) you that your aircraft will have a new personality. More responsive as well as CA Hinges are now double protected. Chances of High speed flutter has reduced 50 %. Hope this makes a little sense. If not I'll be a little more eliquent/literary on the next response.

Anti-Stall Wingtips: They work better with low speed aircraft and Clark Y Airfoils. Reason behind them is a Clark Y is a Flat Bottom wing it's always creating lift as long as the Aircraft is in motion. The 45 deg under cut Tips(Typically called Anti-Stall tips in the hobby) have a self righting tendancy. In other words if you let go of you controls on a bank cut the throttle back and the plane will try to right it self.

(in reply to Volfy)

Wing tip design? - 2/15/2002 1:47:28 PM

slam

Posts: 67
Joined: 1/4/2002
From: BB , BC,
Status: offline

Tip plates reduce the flow from bottom to top at the wing tip and reduce vortex size and therefore drag and therefore improvr performance.

(in reply to Volfy)

Wing tip design? - 2/15/2002 4:46:03 PM

Posts: 656
Joined: 12/3/2001
From: Minot, ND, USA
Status: offline

Ok dennis;
How? Your talking about a 1/16" or 3/32" thick slab of wood on the end of a wing. The Only area it affects is with regards to a vortex is 1/16" or 3/32" at the trailing edge of the Winglet!

(in reply to Volfy)

Wing tip design? - 2/15/2002 5:04:09 PM